LG MA748W 01 Service Manual - Page 11

GENERAL

DETAILS

•

The

low

voltage

transtormer

supplies

the

necessary

—

valtage

-

to

-

the

-

micorn

-

carrtraller

-

when

-

riower

-

card

-

is

plugged

in.

—•-When-the-door-is-closed—the-primany-switch-is-ON—the

secondary

switch

is

ON,

and

the

monitor

switch

opens

contact

COW

and

NO).

•

A

ta

e

of

aooroximately

2

00

vo

t6

AC

is

generated

in

the

secondary

of

the

high

voltage

transformer

which

is

increased

by

the

action

of

the

high

voltage

diode

and

charging

of

the

high

voltage

capacitor

•

The

negative

4,000

Volts

DC

is

applied

to

the

filament

of

the

macnetron.

WHEN

SELECTING

COOKING

POWER

WHEN

THE

OVEN

IS

SET

AT

ANY

LEVEL

-•-The

-micom-controller-memorizes-the--function-you-set-

--MleOrn-controller_controls_the_ON-OFF__time_of_

T

le

time

you

set

appears

in

t

disp

ay

window.

•

Each

indicator

light

turns

on

to

indicate

that

the

stage

as

been

set.

relay

2

by

the

applied

signal

to

vary

the

average

output

power

of

microwave

oven

as

(refer

to

page

1-1)

One

comp

VEL.

ete

cyc

e

of

re

ay

2

is

22

seconc

•

The

coil

of

thc

relay

is

cncrgizcd

by

thc

micom

controller.

WHEN

THE

DOOR

IS

OPENED

DURING

COOKING

•

Power

input

is

supp

ied

to

the

high

vo

tage

transformer

through

thc

fuse

to

thc

primary

switch

and

re

•

Turntable

rotates.

ay

2.

•

Both

the

primary

switch

and

relay

2

arc

cut

off

primary

winding

voltage

of

the

high

voltage

transformer.

•

ON

-OFT

of

relay

2

is

coupled

electrically

with

opening

and

closing

of

the

secondary

switch.

7

N

•

When

the

c

O

oor

is

openec

,

the

secondary

switch

is

Dened

and

when

the

door

is

closed,

the

secondary

switch

is

closed.

L

FUSE

SWITCH

0

H.V.

TRANS

FORMER

•

T

le

coo

•cing

time

stops

counting

down.

•

Relay

stops

functioning.

•

As

the

door

is

opened,

if

the

contact

of

primary

switch

PRIMARY

RELAY

2

SWITCH

SECONDARY

o

----t5

SWITCH

and

relay

2

and/or

secondary

switch

fails

to

open,

the

fuse

opens

due

to

the

the

monitor

switch

activation,

which

in

turn

stops

arge

current

surge

caused

by

gnetron

osci

lation.

MICOM

CONTROLLER

N

0

•

The

fan

motor

rotates

and

coo

s

le

magnetron

by

blowing

the

air

(coming

from

the

intake

on

the

baseplate)

L

MONITOR

SWITCH

H.V.

TRA

NS-

•

The

air

is

also

directed

into

the

oven

to

exhaust

the

vapor

in

the

oven

through

the

upper

plate.

•

Cooking

time

starts

counting

down.

•

3

2

volts

AC

is

generated

from

the

filament

winding

of

FUSE

1:3

0

0

PRIMARY

SWITCH

RELAY

2

O__-(5

S

S

W

EC

IT

O

C

N

H

DARY

the

high

voltage

transformer.

This

3.2

volts

is

applied

to

e

magnetron

to

neat

the

magnetron

tilament

tnroug

two

noise

preventing

choke

coils.

MICOM

CONTROLLER

4-5

LG MA748W 01 Service Manual - Page 11

General, Details, Selecting, Cooking, Power, Level, Opened, During

Page 11 highlights